Good nursery or other place to find inexpensive plants/trees for sale (or free!) in the East Bay?

I’m looking specifically for potted trees that can live indoors.

I’m not familiar with East Bay nurseries, and besides those I’m not sure of other good sources of plants. Today I was at Ace Hardware which had quite a lot of outdoor flowers, and heard that the Longs’ down the street has a lot of plants, and cheaper, which surprised me. Should I craigslist/freecycle this? Another alternative like farmer’s/flea market, a dump, a place like Urban Ore that’s got plants…....?

Oakland would be best, East Bay is ok, and even SF if there’s a good spot.